After years of hard work, Elena (a composite of several women) was up for a long-deserved promotion. But when she returned to work following the birth of her second child, her supervisor began to question whether the new position was “really the kind of job for someone with two little ones at home.” Now that she was a mom, he suggested, her “priorities have changed and she appeared less committed to her job.”

Similarly, Jaqui (also a composite) was a top salesperson who never had problems at work. After she returned from maternity leave, however, her supervisor denied her flextime, overly scrutinized her work performance and gave her a tepid performance review.

Until recently, this treatment—which working mothers are all too familiar with—was not recognized as unlawful gender discrimination. Employers who allowed biases about women’s ability to balance home and work infect their employment decisions were often let off the hook, especially if a woman plaintiff couldn’t compare her treatment to that of men in similar positions at her workplace—as is often the case in smaller or female-dominated businesses. However, thanks to some recent court cases, this form of discrimination is finally becoming recognized as illegal.

Although the term is new, “family responsibilities discrimination” (FRD) has long interfered with the progress of millions of working women who care for children, or elderly or ill family members. As Joan Williams, a leading expert in the field of women and work, and director of the Center for WorkLife Law at University of California Hastings College of the Law, explains, “Family responsibilities discrimination, especially against mothers, is pervasive. While the glass ceiling still exists, most women hit the ‘maternal wall’ long before they ever hit the glass ceiling.”

According to Professor Williams, that wall reflects unexamined assumptions about how women will behave once they become mothers. Those stereotypical assumptions tend to arise when a woman announces her pregnancy or her plans to adopt, when she returns from maternity leave or when she switches to a flexible work arrangement. The bias can be expressed in a hostile manner, as when an employer fires a woman returning from maternity leave, or with ostensible benevolence, as when an employer changes a mother’s duties to require less travel, or denies her a promotion because the new position would require more time at work.

Social-science research confirms that women who have had no problems in the workplace often face employer concerns that they are no longer as committed or competent after they become moms. Performance appraisals suffer, promotions grind to a halt and career-enhancing assignments decline. Experiments conducted by Shelley Correll, an associate professor of sociology at Cornell University, found that mothers are 44 percent less likely to be hired than non-mothers with similar resumes, and were offered an average of $11,000 less than equally qualified non-mothers. In Correll’s experiments, mothers were rated by potential employers as less competent and less committed to their jobs, judged by harsher standards, and seen as less suitable for management positions than women without children. In contrast, the research found that fathers were advantaged by their parenthood status as compared to non-fathers: They were judged by more lenient performance standards, rated as more committed to their jobs and offered higher starting salaries.

After years of slow progress, the law in this area seems to be rapidly developing:

Since the Supreme Court’s 1989 decision in Price Waterhouse v. Hopkins, it has been illegal for employers to discriminate based on stereotypes about how women should behave. Recently, that prohibition has been extended to protect women who are treated differently at work on the basis of stereotypes about their roles as caregivers/mothers.

In its 2003 decision, Nev. Dep’t of Human Res. v. Hibbs (which upheld certain provisions of the Family and Medical Leave Act), the Supreme Court explicitly acknowledged that gender stereotypes of motherhood and caregiving lead to discrimination in the workplace. The Court noted that stereotypical views about women’s domestic responsibilities are reinforced by parallel stereotypes presuming a lack of domestic responsibilities for men, and those biases negatively influence employers’ views about women’s value as employees and their commitment to their work.

In a 2004 case,Back v. Hastings on Hudson Union Free School District,a federal appeals court concluded that an employer’s reliance on stereotypical assumptions about a mother's commitment to her job constitutes sex discrimination. Elana Back, a school psychologist who had terrific reviews before having a child, was denied tenure after she returned from maternity leave. Her employer told her, according to Back, that it was “not possible for [her] to be a good mother and have this job,” and questioned how she planned “on spacing [her] offspring.” In deciding for Back, the court ruled that she did not have to prove that her employer treated similarly situated fathers differently—it was enough to show that the employer relied on gender biases.

In another recent case, Plaetzer v. Borton Automotive, a Minnesota federal court ruled that a woman car salesperson, married with four children, could take her sex discrimination case to trial based on evidence that her supervisor made comments about how his wife did not have child-care problems and that the salesperson should “do the right thing” and stay home with her kids. The supervisor told her that she would always be at a disadvantage at the dealership because she was a woman with a family.

The results of such family responsibilities discrimination cases are promising. The center for WorkLife Law has created a database to track such cases nationally, and has documented nearly a 400 percent increase in cases over the previous decade. The Center reports that plaintiffs are significantly more likely to have a favorable outcome in family responsibility cases than in other types of employment discrimination, winning on average $100,000. And that’s all the more reason for employers to watch their biases—because ultimately it will affect their bottom lines.

Employees concerned about family responsibilities discrimination in the workplace can call the Center for WorkLife Law hotline, (800) 981-9495. Employers who want to prevent FRD can obtain a model policy from www.worklifelaw.org.